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Abstract. In an effort to develop a cellular model for studying cytokinin action in higher plants, we investigated the effect of cytokinins on growth and membrane transport in root hairs of alfalfa (Medicago sativaL.) seedlings. Alfalfa seedlings grown for 24h in the presence of cytokinins showed increased root hair length and formation of root hairs close to the root cap. Increased growth of root...
Abstract.O--D-Galactopyranosyl-(12)-D-chiro-inositol, herein named fagopyritolB1, was identified as a major soluble carbohydrate (40% of total) in buckwheat (Fagopyrum esculentum Moench, Polygonaceae) embryos. Analysis of hydrolysis products of purified compounds and of the crude extract led to the conclusion that buckwheat embryos have five -galactosyl D-chiro-inositols: fagopyritolA1 and fagopyritolB1...
Abstract. Cytosolic NADP-dependent isocitrate dehydrogenase (cyt-NADP-ICDH; EC 1.1.1.42) has been suggested to play a major role in the production of 2-oxoglutarate, an important precursor for amino acid synthesis. Using an antisense RNA approach under the control of the cauliflower mosaic virus 35S promoter, transgenic potato plants were created in which NADP-ICDH activity was reduced to 8% of the...
Abstract. A member of a eukaryotic gene superfamily, encoding a peptidylproline cis-trans-isomerase (rotamase) has been isolated from a maize (Zea mays L. A69Y+) endosperm cDNA library. The maize sequence (mzFKBP-66) encodes a 66-kDa polypeptide most closely related to the subclass of rotamases which bind an immunosuppressive drug, FK506, (termed FK506-binding proteins, FKBPs), and possesses four...
Abstract. Rice (Oryza sativa L.) phloem sieve tubes contain RPP13-1, a thioredoxin h protein that moves around the plant via the translocation stream. Such phloem-mobile proteins are thought to be synthesized in the companion cells prior to being transferred, through plasmodesmata, to the enucleate sieve-tube members. In this study, in-situ hybridization experiments confirmed that expression of RPP13-1...
Abstract. The arabinogalactan protein-binding -d-glucosyl Yariv reagent (GlcY) was applied to the various developmental stages of embryogenic carrot (Daucus carota L. cv. Early Nantes) cell-suspension cultures. Roots without shoot structures were produced in cultures grown under embryo-inducing conditions in medium containing GlcY. Only low concentrations of GlcY permitted the subsequent production...
Abstract. The organization of the microtubule (MT) and actin microfilament (MF) cytoskeleton of tip-growing rhizoids and protonemata of characean green algae was examined by confocal laser scanning microscopy. This analysis included microinjection of fluorescent tubulin and phallotoxins into living cells, as well as immunofluorescence labeling of fixed material and fluorescent phallotoxin labeling...
Abstract. Iron-deficiency-induced protein A (IdiA) with a calculated molecular mass of 35kDa has previously been shown to be essential under manganese- and iron-limiting conditions in the cyanobacteria Synechococcus PCC 6301 and PCC 7942. Studies of mutants indicated that in the absence of IdiA mainly photosystem II becomes damaged, suggesting that the major function of IdiA is in Mn and not Fe metabolism...
Abstract. In leaf tissues of the Cichorium hybrid clone `474 (C. intybus L. var. sativumC. endivia L. var. latifolia), the acquisition and expression of embryogenic competence was characterised by the appearance of 15 polypeptides (Boyer et al., 1993, Plant Sci 93: 4153). The 38-kDa proteins were found to be abundantly present in conditioned embryogenic medium after the first division of the induced...
Abstract. We have investigated the possibility that vacuolar proteins can be secreted into the medium of cultured cells of Nicotiana tabacum L. Time-course and balance-sheet experiments showed that a large fraction, up to ca. 19%, of vacuolar -mannosidase (EC 3.2.1.24) and vacuolar class I chitinase (EC 3.2.1.14) in suspension cultures accumulated in the medium within one week after subculturing....
Abstract.Tillandsia usneoides L. is a favorite model plant for investigating ethylene biosynthesis because no soil is needed for cultivation (important for long-term measurements) and small plants and different clones are available. We investigated the endogenous production of ethylene in relation to temperature, light, daylength and CO2 concentration. Using a novel and most sensitive technique to...
Abstract. Treatment of suspension-cultured potato cells (Solanum tuberosum L. cv. Desire) with an elicitor from Phytophthora infestans induced increased incorporation of 4-hydroxybenzaldehyde, 4-hydroxybenzoate, and N-4-coumaroyl- and N-feruloyltyramine into the cellwall and secretion of N-4-coumaroyl- and N-feruloyltyramine into the culture medium. Induced metabolite accumulation was preceded by...
Abstract. Double-barrelled nitrate-selective microelectrodes have been used to measure the time course of the remobilisation of vacuolar stored nitrate in barley (Hordeum vulgare L. cv. Klaxon) root cells during 24h of nitrate deprivation. These measurements showed that there are different time courses for this process in epidermal and cortical cells of the same root. The remobilisation was much slower...
The sucrose concentration was measured at 70-min intervals in the phloem of individual bundles of the hypocotyl of Ricinus seedlings by 1H nuclear magnetic resonance (NMR) spectroscopic imaging. The sucrose concentration stayed fairly constant in all bundles for more than 7h if the cotyledons were embedded in the endosperm or excised and incubated in 100mM sucrose. If, however, the sucrose solution...
Abstract. The apoplastic pH of guard cells probably acidifies in response to light, since light induces proton extrusion by both guard cells and epidermal leaf cells. From the data presented here, it is concluded that these apoplastic pH changes will affect K+ fluxes in guard cells of Arabidopsis thaliana (L.) Heynh. Guard cells of this species were impaled with double-barrelled microelectrodes, to...
Abstract. A cytosolic and a plastidic isoenzyme of glutamine synthetase (GS; EC 6.3.1.2) were separated from hairy roots of Beta vulgaris L. var. lutea. The predominant activity was that of cytosolic GS 1; the relative proportion of plastidic GS 2 activity changed, however, depending on the growth conditions. Maximum activity of both isoenzymes was measured after growth with NO3 as the major N-source...
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